(a) Field of the Invention
The present invention relates to a swim fin, and more particularly to a swim fin having an energy-conserving function, wherein energy-conserving devices with springs are fitted to a swim fin, thereby enabling a swimmer to conserve energy when swimming, and thus increasing staying power to move forward and reducing probability of foot cramp.
(b) Description of the Prior Art
Referring to FIG. 1, which shows a conventional swim fin, wherein a blade 200 extends from a front portion of a foot pocket 100, and two sides of the blade 200 are respectively provided with a columnar body 201 to provide support for the swim fin. When a swimmer is in the water and moving his two feet up and down to force the swim fin into a two-stroke alternate flapping motion, the swimmer is able to kick the water to propel forward, and the support provided by the columnar bodies 201 enables the blade 200 to form an angle against the water to achieve a propulsion effect. Furthermore, when the flapping motion returns the swim fin back to its original state, the columnar bodies 201 still provide the same force coefficient for the blade 200 to form an angle against the water, thereby causing energy consumed in the restoring motion of the swim fin and kicking of the water to propel forward is the same. The angle against the water causes the restoring motion to slow down, and after a long period of use, because energy consumed by the alternate flapping motion of the swim fin is the same, thus, physical strength of the swimmer is easily overdrawn, which results in poor staying power, moreover, there is the danger of cramp easily occurring in the foot, especially when there is the need to speed up the alternate flapping motion to counteract adverse currents, which clearly reveals the need for improvement.